Interpolating device



May 14, 1935' A. P. BEREJKOFF INTERPOLATING DEVICE Filed Jan. 18, 1934reauny Ind/:atar

Patented May 1.4, 1935 UNITED STATES INTERPOLATING DEVICE Anatole P..Berejkoi, SchenectadygN. Y., as-

signor to General Electric y ration of New York Company, a, corpo-A'ppiication January 1s, 1934, seriai No. 707,230 claims. (01. 25o-39)AMy invention relates tointerpolating. devices and more particularlytosuch devices for use in connection with heterody'ne frequencyindicating systems. i i

5 Inheterodyne frequency indicating systems an oscillation generator iscommonly employedhaving a Afrequency which is, adjustable over the rangeof frequencies which it is desired to indicate.y The frequency adjustingdevice of this oscillator, which I shall herein refer to as vthe localoscillator commonly is calibrated in terms of frequency, or in arbitraryterms, which may be interpreted into terms of frequency by reference toa proper calibration chart `or curve.

To determine thefrequency of oscillations the frequency of which isunknown, oscillations from the local oscillator are caused to vcombinewith the unknown oscillations to produce a beat note. I'his beat note isdetected in any-suitable way as by means of headphones. 'Ihe localoscillator is then so adjusted that the beat note disappears or becomesofl zero frequency. 'I'he unknown frequency is then equal to thefrequency of the local oscillator` and may be determined from thecalibrationof they local oscillator.

y Difficulty is experienced, however, in determining the exactadjustment of the local oscillator at which the zero beat is produced.Thisis due to the fact that the earis insensitive tofrequencies 30 inthe neighborhood of zero. Because of this difficulty it is common so toadjust the local oscillator that a beat frequency of definitelyrecognizable frequency is produced, read the dial, then turn theadjusting device through the zero beat position to a position in whichthe same definitely recognizable frequency is produced, and lthen againread the dial. The zero beat position may then be determined byinterpolating between .A jects and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying drawing in which Fig. l represents the calibrationdials employedin accordance with my invention; Fig. 2 shows meanswhereby these dials are intercon nected; and Fig. 3 indicates the use ofmy in` vention in a system for frequency determination. The rectangle ofFig. 3 of the drawing repre-'- sents a frequency indicator comprising alocal os'- cillator the frequency of which is adjusted by means of anadjusting device 2 and to which oscillations of unknown frequency may besuppliedby means of a connection which is conventionally shown in thedrawing as an antenna 3. These oscillations are caused to combine,either in the local oscillator itself, or in a separate detector, asdesired, with the oscillations produced by the local oscillator therebyto produce a beat note which may be detected by means of the head'-phones 4. The frequency adjusting device 2 of the oscillator may ofcourse be connected with anyv suitable frequency determiningY element ofthe oscillatorcircuit such as a reactance or condenser which is soconstructed as to produce a corresponding frequency change, and is pro'vided with a number of dials indicated by the circles 5 rand 6wherebythe frequency. produced by the local `oscillator may be determined.

.These dials 5 and 6 are better shown in Figs. 1 and 2. They arecalibrated about their periphery as indicated in Fig. 1 and havecooperating therewith hair lines 'I and 8 respectively which are carriedupon members which are fixed to the shafts of the frequency determiningdevice, and rotatable over the dials 5 and 6.. This isrbetter shown inFig. 2 where the dials 5 and 6 are shown as fixed to the mounting panelof the apparatus by means of screws 9- and` I0 and in. which are shownplates I I and I2 which are adapted for rotation over thedials 5 and 6respectively. 'I'he circular plates II and l2, of course,`carry upontheir inner surfaces, adjacent to dials 5 and lIi, the hair lines 'I and8. These'plates are securely attached to shafts I3 4and I4, the latterof which is provided withy a knob I5 having a projection I 5 thereonwhereby it may be readily rotated by the finger of the operator. Thisshaft I4 carriesa .worm gear I6 which cooperates with la worm wheel I6mounted upon the shaft I'I of a variable condenser I8, the latter ofwhich may comprise the frequency determining element of vthe localoscillator. The shaft I 3' carrying the the member I 2 is moved over thedial 6, and further that the hair line on the member I I is movedr overthe scale 5.

'I'he particular calibration illustrated on the` scales vand 6 and thegear ratio between the respective hair line carrying members I I and I2is such that the entire frequency range over which it is desired, withthe instrument illustratedto indicate frequencies is divided vinto 2500.equal parts. This will be seen from the facts that the scale of the`dial 5 extends 'only' over a semi-cir.- cumference which is dividedinto twenty-live equal parts, whereas the scale of dialv ljsdlvided intotwo semi-circumferences each of vwhich is.I divided into one hundredequal partgwhile the these scales land a proper frequency calibrationchart-the local ,oscillator canbeadjusted to prol duce anyv desiredVfrequency withinthe range.

l Een .exaxnple, Aletussuppose that'it is desired .to the frequency .ofthe local .oscillator for V305000 kilocycles and .that our calibrationcurve :or .chart .gi-vesthe scale reading corresponding to thisfrequency 95.11255. Theknob I5 will then be rotated luntil the hairline`1 occupies the position corresponding :to ,12 plusgand thehairline Boccupies the position: corresponding to 55. The frequency of the.oscillator will then be 30,000 kilQCycles.. It `is .observed that theunits and tensydigits A.of the dial reading .are read rIromthe dial Sand.the hrundredsandthousands digitsy are 4'need fromthe dial 5;' Y 1- i vj YIn determining the unknown frequency'ofoscillati'ons received Aon.the antenna 3, for example, 1t will of course'ibe understood,as'pointed out -ahoie,'thatltheiknob .Ii is rotated until a' denite- 'lyrecognizable beat .note isV obtained.y The dials maythen 'be-read; andfthe knob I 5 again rotated,

threugh'the zero Abeat, position, until the same denrtely recognizablefrequency vis obtained. lilac V.dial is thenlagain read; Were lnoA iother means .provided it would lbe necessary to 'inter- 'mie betweenthese two dial readings to obtain ,the exact dial "reading correspondingto the positinifofthe zero-beat. Inzorder that tl'iis .zero heatposition may beread `directly from the instnumenttwo additional dialsareprovided, these .dials ibeing'indicated .at 22 vand. 22?w These dials'arezeoncentric with .the dials 5 and 6 respectively ,andhavecalibrations about their inner periphery togceoperate withthecalibrationsof thedials 5 and .6. yThese dialsyarealso serrated'about their .outer periphery as shown at 23 so that. they may bevreadily `grasped .by the hand -of ,the operator. and rotated. Theirarrangement in the appara- 1511.5" vis further illustrated inv Fig. 2where they are Shown lsely tted with vilh'erdial.members 5 and l Yandarranged for free ,rotation :about the Vdials 5, and 5 l Y f y .Y 1twill be observed thatthe `inner periphery `of `,each of thefdialsY 22yand 22 vare zdivided in divisions of value equal to the divisionsy of.the scalel 5, 6 respective1y,`but`that the scale divisions of the dials22 and`22 are each of double `the length of vthe rscale divisionsy ofthe .6.113115 5 and 6. VThus .whileasemi-circumfollowing manner. I5until he vhears a definitely recognizable fre- `1180 oflthe outer dial.v

ference of the dial 5 ,is divided into twenty-five equal parts theentire circumference of the dial 22 is divided into twenty-five equalparts. Similarly while the circumference of the dial 6 is divided intotwo hundred equal parts, the entire circumference of the dial 22 isdivided into one hundred equal parts.

. position of. zero heatbetmeen the oscillations produced byfthe loca-1osillatorandreceived oscillations of unknown frequency may now `bedetermined immediately from the` scales in the The operator turns theknob queIlCy in the headphones l. He then moves both of the outerdialstosuch positions that the readings of` the-outer dials under the hairlines is the same as the readings of the inner correspondingY dialsrund'er-tie'lluair line. v`He then moves Alocal .oscillator toproducethe zero beat he will` then -set the hair lines "to theintermediate position on the inner ydials which read' the same. as

the; lastprevious reading on' thelouter dials.""'

nitelyrecognizable irequencyfat acertainposition. vAssu'methat thereadings of the inner'- dials 'are then 1250. He sets the outerdialsat--this same reading. He then rotates the knob I5 until pose thatIthis is at thepositionwhere the inner ndials read 1110. The outer'dialsWill'thenfread 1180 which corresponds to the reading on `the inner -dialexactlyL half way-between the 1-1'10and 1250 calibrations; Thus ltheunknown frequency Amay .be determined directly from the 4reading It mayhappen,fhowever, in' interpreting the zero reading, that is, in`theexample given, `the reading'- 1180, `into terms vof frequency,-thatfwe mayfnd thatthe-'chart' doesnot give the exact frequencycorresponding to thisv particularreading. For -examplethe' chart 'maygivey 'a K4ire,- quency, for example fr, correspondingfto a'dial readingof, let us say, 520 and a diITeren'tfrequency f2 corresponding to a dialreading'of 1620, no intermediate dial rreadings being giveng.l Itisnecessary: therefore to calculate the Y frequency corresponding -to thereading 1180 yfrom the caiibration points 520 and 1620 given bythechart. The outer dials have beenV found to be vextremely useful ineffecting this calculation.` VInueffecting this calculation by the useofthe dials theoperator rst sets thehair lines at the reading'520 of theinner dials. He then sets the zeros of .the outer dials underthe hairlines. He then moves the hair lines to the reading `1180 on-theinnerdials and notes the reading of the outer dial. This reading vmay be 330.He then moves VAthe hair lines tothe upper calibrationppoint i620 givenby the chart and again reads Vthe .outer dials. Let ussay that thisreading is y55.0.*4 rThe unknown frequency is `then f presented by wayof clearly indicating the principles involved and is applicable only inthe event that the frequency determining device has a linear operatingcharacteristic. My invention,

however, is in no wise limited to the particular calibration, or form ofcalibration, shown. For example, the condenser I8 may be one whichvaries the frequency of the oscillator in a nonlinear manner, as, forexample, logarithmically. The dials 5 and 6 as thus employed will becalibrated accordingly and the outer dials simiylarly calibrated withscales of suitably greater example a filter maybe included in thecircuit of the headphones which is sharply resonant at the beatfrequency to be passed whereby the desired beat frequency is heard inthe headphones with a maximum intensity. Furtheran additional localoscillator of audio frequency may be employed, the oscillations of whichare caused to lbeat with the low frequency oscillations the frequency ofwhich is to be recognized. In this way the local high frequencyoscillator may be adjusted until zero beat between the twor lowvfrequencies is produced, this point being very readily recognizable byuse of the headphones.

yAny other means to facilitate the recognizing of a definite frequency`may of course be employed.

While I have shown a particular embodiment of my invention it will ofcourse be understood that I do not wish to be limited thereto sincevarious modifications may be made both in the operating mechanism shownand in the scales illus-y trated without departing from the spirit andscope of my invention. I therefore contemplate by the appended claims tocover any such modifications as fall within the true spirit and scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the'UnitedStates is:

1. The combination of means to produce a beatfrequency betweenoscillations the frequency of which is to be indicated and otheroscillations, means including a variable position device to control thefrequency of said other oscillations to produce a zero beat in a certainposition of said variable position device and a definitely recognizablebeat when said variable position device is in positions on either sideof said certain position and removed therefromv by equal distances, anindex for said variable position device movable over a fixed calibratedscale, a movable calibrated scale cooperating with said fixed movablescale.

ing ycalibration on the movable'scale to the same position, then movingthe index to the other position where the recognizable beat is producedand determining the frequencyk from the 2. In a frequency indicatingdevice, the combination of means to produce a beat frequency betweenoscillations the frequency of which is to be indicated and otheroscillations, means includ-`v ing avvariable position device to controlthe frequency of said other oscillations to produce a zero beat ina-certain position of said variable position device and a readilyrecognizable frequency in other positions of said variable positiondevice on either side of said certain position and spaced therefrom byamounts determined by the law of operation of said means, an index forsaid variable position device movableover a fixed calibrated scale and amovable calibrated scale, said movable calibrated scale cooperating withsaid xed scale and having calibrations bearing a relation to thecalibrations on the fixed scale determined by said law of operation ofsaid means,

said movable scale being movable to bring any calibration thereon tocoincide with a corresponding calibration on the fixed scale, wherebythe desired frequency may be determined from the movable scale.

3. In combination, a variable position device, means for interpolatingbetween different positions of said device, said means comprising anindex movable over 'a fixed calibrated scale whereby the differentpositions to be interpolated between may be noted a movable scalecooperating with said fixed scale and said index, and havingcalibrations thereon which bear a relation to the calibrations on saidfixed scale determined by the interpolation to be effected, whereby bymoving said index to a point on the fixed scalev corresponding to one ofsaid positions, moving the corresponding point on theA movable scale tocoincide therewith and then moving the index to a point on the fixedkscale corresponding to the 'corresponding to other calibrations of saidscaley intermediate said certain calibrations, said means comprising ascale cooperating with said first mentioned scale, said last mentionedscale' having calibrations thereon extending from Zero upwardv in termsequivalent to the calibrations of said first scale, said secondmentioned v,scale being movable to bring the zero calibrations adjacentany of said certain calibrations on said first scale,A

and an index movable over both of said scales.

ANATOIE P. BEREJKOFF.

